1. Field of the Invention
The present invention relates to a host channel adapter configured for communication with target channel adapters in an InfiniBand™ server system, and more particularly to the servicing by the host channel adapter of work notifications, also referred to as “doorbells”, that notify the host channel adapter of work queue entries to be serviced.
2. Background Art
Networking technology has encountered improvements in server architectures and design with a goal toward providing servers that are more robust and reliable in mission critical networking applications. In particular, the use of servers for responding to client requests has resulted in a necessity that servers have an extremely high reliability to ensure that the network remains operable. Hence, there has been a substantial concern about server reliability, availability, and serviceability.
In addition, processors used in servers have encountered substantial improvements, where the microprocessor speed and bandwidth have exceeded the capacity of the connected input/output (I/O) buses, limiting the server throughput to the bus capacity. Accordingly, different server standards have been proposed in an attempt to improve server performance in terms of addressing, processor clustering, and high-speed I/O.
These different proposed server standards led to the development of the InfiniBand™ Architecture Specification, (Release 1.0), adopted by the InfiniBand™ Trade Association. The InfiniBand™ Architecture Specification specifies a high-speed networking connection between end nodes (e.g., central processing units, peripherals, etc.) and switches inside a server system. Hence, the term “InfiniBand™ network” refers to a private system area network (SAN) that connects end nodes and switches into a cluster within a server system, enabling the sharing of cluster resources. The InfiniBand™ Architecture Specification specifies both I/O operations and interprocessor communications (IPC).
A particular feature of InfiniBand™ Architecture Specification is the proposed implementation in hardware of the transport layer services present in existing networking protocols, such as TCP/IP based protocols. The hardware-based implementation of transport layer services provides the advantage of reducing processing requirements of the central processing unit (i.e., “offloading” processor code execution), hence offloading the operating system of the server system.
However, arbitrary hardware implementations may result in substantially costly or relatively inefficient hardware designs. One example involves the servicing of work notifications, also referred to as “doorbells”. Doorbells are generated by verbs consumers (e.g., operating system supplied agents) that post a work request, for example a work queue entry (WQE) in system memory; the verbs consumer then sends the work notification to notify the host channel adapter of the work request in system memory.
Typically the host channel adapters are configured for servicing work notifications sequentially, using a first in first out arrangement. However, the link layer operations within the HCA are configured for transmitting InfiniBand™ packets according to virtual lane prioritization, for example a weighted round robin virtual lane prioritization. Hence, instances may arise where the host channel adapter may service work notifications for work requests associated with a virtual lane having a relatively low priority. Consequently, transport layer resources and link layer resources within the channel adapter are not coordinated relative to the link layer prioritization, resulting in inefficient utilization of resources. In addition, such uncoordinated operations between the transport layer resource and link layer resources limit the ability of the HCA transferring packet data for data streams (e.g., real time streaming data for video, voice, audio, etc.) according to Quality of Service policies preferred by the provider or consumer of the data streams.